Cortico-cortical connectivity of the human mid-dorsolateral frontal cortexand its modulation by repetitive transcranial magnetic stimulation

Modulation of cortico-cortical connectivity in specific neural circuits mig ht underlie some of the behavioural effects observed following repetitive t ranscranial magnetic stimulation (rTMS) of the human frontal cortex. This p ossibility was tested by applying rTMS to the left mid-dorso lateral fronta l cortex (MDL-FC) and subsequently measuring functional connectivity of thi s region with positron emission tomography (PET) and TMS. The results showe d a strong rTMS-related modulation of brain activity in the fronto-cingulat e circuit. These results were confirmed in a parallel experiment in the rat using electrical stimulation and field-potential recordings. Future studie s are needed to provide a direct link between the rTMS-induced modulation o f cortical connectivity and its effects on specific behaviours.